feat: add anime metadata editing and NFO diagnostics

- Add PUT /anime/{key} endpoint for updating anime key, tmdb_id, tvdb_id
- Add NFO diagnostics and repair endpoints (GET/POST /nfo/diagnostics)
- Add edit modal UI with context menu integration
- Add frontend JS modules for context-menu and edit-modal
- Add comprehensive tests for edit, rename, and NFO repair flows

src/server/api/anime.py

@@ -17,12 +17,14 @@ from src.server.exceptions import (
     ServerError,
     ValidationError,
 )
+from src.server.models.anime import AnimeMetadataUpdate
 from src.server.services.anime_service import AnimeService, AnimeServiceError
 from src.server.services.background_loader_service import BackgroundLoaderService
 from src.server.services.folder_rename_service import _scan_for_pre_existing_duplicates
 from src.server.utils.dependencies import (
     get_anime_service,
     get_background_loader_service,
+    get_database_session,
     get_optional_database_session,
     get_series_app,
     require_auth,
@@ -1186,3 +1188,75 @@ async def get_anime(
 # Maximum allowed input size for security
 MAX_INPUT_LENGTH = 100000  # 100KB
 
+
+@router.put("/{anime_key}")
+async def update_anime_metadata(
+    anime_key: str,
+    body: AnimeMetadataUpdate,
+    _auth: dict = Depends(require_auth),
+    db: AsyncSession = Depends(get_database_session),
+) -> dict:
+    """Update anime metadata (key, tmdb_id, tvdb_id).
+
+    Args:
+        anime_key: Current series key to update
+        body: Fields to update (all optional)
+        _auth: Authentication dependency
+        db: Database session
+
+    Returns:
+        Updated series metadata
+
+    Raises:
+        HTTPException 404: Series not found
+        HTTPException 409: Key conflict (new key already exists)
+        HTTPException 422: Validation error
+    """
+    series = await AnimeSeriesService.get_by_key(db, anime_key)
+    if not series:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=f"Series with key '{anime_key}' not found",
+        )
+
+    updates = {}
+
+    if body.key is not None and body.key != anime_key:
+        existing = await AnimeSeriesService.get_by_key(db, body.key)
+        if existing:
+            raise HTTPException(
+                status_code=status.HTTP_409_CONFLICT,
+                detail=f"A series with key '{body.key}' already exists",
+            )
+        updates["key"] = body.key
+
+    if body.tmdb_id is not None:
+        updates["tmdb_id"] = body.tmdb_id
+
+    if body.tvdb_id is not None:
+        updates["tvdb_id"] = body.tvdb_id
+
+    if not updates:
+        return {
+            "key": series.key,
+            "tmdb_id": series.tmdb_id,
+            "tvdb_id": series.tvdb_id,
+            "message": "No changes",
+        }
+
+    updated = await AnimeSeriesService.update(db, series.id, **updates)
+    await db.commit()
+
+    logger.info(
+        "Updated metadata for '%s': %s",
+        anime_key,
+        updates,
+    )
+
+    return {
+        "key": updated.key,
+        "tmdb_id": updated.tmdb_id,
+        "tvdb_id": updated.tvdb_id,
+        "message": "Metadata updated successfully",
+    }
+